Easy factoring question

[kevind147]

Can someone walk me through factoring this:

x^4 - 10x^2 + 9

The answer is (x+3)(x-3)(x+1)(x-1), but I don't know how to get there.

[scoobydooby]

x^4 - 10x^2 + 9
=> x^4-9x^2-x^2+9
=>x^2(x^2-9)-1(x^2-9)
=>(x^2-9)(x^2-1)
=>(x+3)(x-3)(x+1)(x-1)

[lilu]

You can factor it into (x^2 - 9) ( x^2 -1).
Then-->
(x -3)(x+3)(x-1)(x+1)

[kevind147]

good lord, that was fast. i told you it was easy! thanks guys! i need to learn to look at this stuff from different angles ...